Ornithine decarboxylase, mitogen-activated protein kinase and matrix metalloproteinase-2 expressions in human colon tumors

The FnBPA from methicillin-resistant Staphylococcus aureus promoted development of oral squamous cell carcinoma

Background

Oral squamous cell carcinoma (OSCC) is the most common tumor in the oral cavity. Methicillin-resistant Staphylococcus aureus (MRSA) were highly detected in OSCC patients; however, the interactions and mechanisms between drug-resistant bacteria (MRSA) and OSCC are not clear.

Aim

The aim of this study was to investigate the promotion of MRSA on the development of OSCC.

Methods

MRSA and MSSA (methicillin-susceptible) strains were employed to investigate the effect on the proliferation of OSCC in vitro and vivo.

Results

All of the MRSA strains significantly increased the proliferation of OSCC cells and MRSA arrested the cell cycles of OSCC cells in the S phase. MRSA activated the expression of TLR-4, NF-κB and c-fos in OSCC cells. MRSA also promoted the development of squamous cell carcinoma in vivo. The virulence factor fnbpA gene was significantly upregulated in all MRSA strains. By neutralizing FnBPA, the promotions of MRSA on OSCC cell proliferation and development of squamous cell carcinoma were significantly decreased. Meanwhile, the activation of c-fos and NF-κB by MRSA was also significantly decreased by FnBPA antibody.

Conclusion

MRSA promoted development of OSCC, and the FnBPA protein was the critical virulence factor. Targeting virulence factors is a new method to block the interaction between a drug-resistant pathogen and development of tumors.

Downregulation of MTAP promotes Tumor Growth and Metastasis by regulating ODC Activity in Breast Cancer

5'-Methylthioadenosine phosphorylase (MTAP) is a key enzyme in the methionine salvage pathway and has been reported to suppress tumorigenesis. The MTAP gene is located at 9p21, a chromosome region often deleted in breast cancer (BC). However, the clinical and biological significance of MTAP in BC is still unclear. Here, we reported that MTAP was frequently downregulated in 41% (35/85) of primary BCs and 89% (8/9) of BC cell lines. Low expression of MTAP was significantly correlated with a poor survival of BC patients (P=0.0334). Functional studies showed that MTAP was able to suppress both in vitro and in vivo tumorigenic ability of BC cells, including migration, invasion, angiogenesis, tumor growth and metastasis in nude mice with orthotopic xenograft tumor of BC. Mechanistically, we found that downregulation of MTAP could increase the polyamine levels by activating ornithine decarboxylase (ODC). By treating the MTAP-repressing BC cells with specific ODC inhibitor Difluoromethylornithine (DFMO) or treating the MTAP-overexpressing BC cells with additional putrescine, metastasis-promoting or -suppressing phenotype of these MTAP-manipulated cells was significantly reversed, respectively. Taken together, our data suggested that MTAP has a critical metastasis-suppressive role by tightly regulating ODC activity in BC cells, which may serve as a prominent novel therapeutic target for advanced breast cancer treatment.

KRAS mutation-independent downregulation of MAPK/PI3K signaling in colorectal cancer

KRAS is a gatekeeper gene in human colorectal tumorigenesis. KRAS is ‘undruggable’; hence, efforts have been diverted to inhibit downstream RAF/MEK/ERK and PI3K/Akt signaling. Nevertheless, none of these inhibitors has progressed to clinical use despite extensive trials. We examined levels of phospho‐ERK1/2(T202/Y204) and phospho‐Akt1/2/3(S473) in human colorectal tumor compared to matched mucosa with semi‐quantitative near‐infrared western blot and confocal fluorescence immunohistochemistry imaging. Surprisingly, 75.5% (25/33) of tumors had lower or equivalent phospho‐ERK1/2 and 96.9% (31/32) of tumors had lower phospho‐Akt1/2/3 compared to matched mucosa, irrespective of KRAS mutation status. In contrast, we discovered KRAS‐dependent SOX9 upregulation in 28 of the 31 (90.3%) tumors. These observations were substantiated by analysis of the public domain transcriptomics The Cancer Genome Atlas (TCGA) and NCBI Gene Expression Omnibus (GEO) datasets and proteomics Clinical Proteomic Tumor Analysis Consortium (CPTAC) dataset. These data suggest that RAF/MEK/ERK and PI3K/Akt signaling are unlikely to be activated in most human colorectal cancer.

p38α Mitogen-Activated Protein Kinase Is a Druggable Target in Pancreatic Adenocarcinoma

p38 mitogen-activated protein kinases are signaling molecules with major involvement in cancer. A detailed mechanistic understanding of how p38 MAPK family members function is urgently warranted for cancer targeted therapy. The conformational dynamics of the most common member of p38 MAPK family, p38α, are crucial for its function but poorly understood. Here we found that, unlike in other cancer types, p38α is significantly activated in pancreatic adenocarcinoma samples, suggesting its potential for anti-pancreatic cancer therapy. Using a state of the art supercomputer, Anton, long-timescale (39 μs) unbiased molecular dynamics simulations of p38α show that apo p38α has high structural flexibility in six regions, and reveal potential catalysis mechanism involving a “butterfly” motion. Moreover, in vitro studies show the low-selectivity of the current p38α inhibitors in both human and mouse pancreatic cancer cell lines, while computational solvent mapping identified 17 novel pockets for drug design. Taken together, our study reveals the conformational dynamics and potentially druggable pockets of p38α, which may potentiate p38α-targeting drug development and benefit pancreatic cancer patients.

The expression of iNOS and nitrotyrosine in colitis and colon cancer in humans

Chronic inflammation increases the risk of development of several types of malignancies including colon cancer. It also represents a paradigm for the connection between inflammation and cancer in terms of epidemiology and mechanistic studies in preclinical models. A key component of inflammation promoting cancer is the transcription factor NF-κB, which is known to play a critical role in the regulation of the inducible nitric oxide synthase (iNOS) gene. iNOS is an enzyme dominantly expressed during inflammatory reactions. Although synthesis of high amounts of nitric oxide (NO) by iNOS has been demonstrated in pathophysiological processes, such as acute or chronic inflammation and tumorigenesis, the role of iNOS activity in these diseases is still not well understood. Analysis of human biopsies of colitis and colon cancer using immunohistochemistry revealed elevated iNOS protein expression levels, which were strongly paralleled by increased expression of nitrotyrosine suggesting that iNOS has been highly activated in these tissues. These results were corroborated in an in vitro study showing the presence of high iNOS levels in a colon cancer cell line (HT-29) following inflammatory stimuli (TNF-α, peroxynitrite). In addition, the involvement of metastatic processes in the colon biopsies was assessed by means of in situ zymography of MMP activation. MMP 2 (gelatinase A) activation was higher in histopathological sections of colitis and cancer compared to controls. Overall, these data strengthen the findings that in inflammation and colon cancer in humans, iNOS expression and tyrosine nitration may be an indicator of cancer development and progression.

KRAS/BRAF mutation status and ERK1/2 activation as biomarkers for MEK1/2 inhibitor therapy in colorectal cancer

Phase II clinical trials of mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitors are ongoing and ERK1/2 activation is frequently used as a biomarker. In light of the mutational activation of BRAF and KRAS in colorectal cancer, inhibitors of the Raf-MEK-ERK mitogen-activated protein kinase are anticipated to be promising. Previous studies in pancreatic cancer have found little correlation between BRAF/KRAS mutation status and ERK1/2 activation, suggesting that identifying biomarkers of MEK inhibitor response may be more challenging than previously thought. The purpose of this study was to evaluate the effectiveness of MEK inhibitor therapy for colorectal cancer and BRAF/KRAS mutation status and ERK1/2 activation as biomarkers for MEK inhibitor therapy. First, we found that MEK inhibitor treatment impaired the anchorage-independent growth of nearly all KRAS/BRAF mutant, but not wild-type, colorectal cancer cells. There was a correlation between BRAF, but not KRAS, mutation status and ERK1/2 activation. Second, neither elevated ERK1/2 activation nor reduction of ERK1/2 activity correlated with MEK inhibition of anchorage-independent growth. Finally, we validated our cell line observations and found that ERK1/2 activation correlated with BRAF, but not KRAS, mutation status in 190 patient colorectal cancer tissues. Surprisingly, we also found that ERK activation was elevated in normal colonic epithelium, suggesting that normal cell toxicity may be a complication for colorectal cancer treatment. Our results suggest that although MEK inhibitors show promise in colorectal cancer, KRAS/BRAF mutation status, but not ERK activation as previously thought, may be useful biomarkers for MEK inhibitor sensitivity.

Identification of gene signatures for invasive colorectal tumor cells

BACKGROUND

Gene signatures of sporadic colorectal carcinoma tissues and microdissected colorectal tumor cells were analyzed to identify stromal and tumor cell-specific markers, respectively.

METHODS

Serial sections of frozen colorectal tumors (n=29) were subjected to RNA isolation of (1) entire tissue sections with a various tumor cell content and of (2) microdissected invasive tumor cells. Three matching samples of microdissected normal colorectal epithelial and invasive tumor cells were similarly obtained. RNA samples were analyzed using the HG95A and HG95Av2 GeneChip microarrays (Affymetrix). The microarray data was evaluated by established methods and validated by Q-RT-PCR.

RESULTS

Unsupervised hierarchical cluster analysis of 18 sample pairs (training set) clearly distinguished tumors from microdissected tumor cells. A 149-gene signature was identified using statistical methods, which was then validated by a hierarchical clustering analysis of 11 independent sample pairs (test set). Genes specifically associated with microdissected invasive tumor cells were for example CKS2 and NME1. In contrast, genes associated with stromal cells were for example MMP2, SDF1 and FBLN2. Finally, a 65-gene signature distinguished normal colorectal epithelial cells and invasive tumor cells, including down-regulation of BMP2 and ANPEP mRNA expression as well as up-regulation of TKT, SPARC, MCM5 mRNA expression.

CONCLUSIONS

Our approach allowed precise evaluation of molecular signatures in morphologically defined cell populations and identified novel target genes related to stroma-tumor interactions in colorectal cancer. The approach enables further analysis of gene signatures in different tumor areas and cell types, such as within invasive margins to decipher molecular mechanisms of colorectal cancer invasion and metastasis.

Ornithine decarboxylase activity as a prognostic marker for colorectal cancer

Ornithine decarboxylase (ODC) is a key enzyme in the biosynthesis of polyamines, which are essential for cell proliferation. ODC activity was measured in 47 colorectal cancer patients, 5 patients with adenoma of colorectum and 4 healthy volunteers. Mean ODC activities of cancer tissue, non-cancerous mucosa from cancer-bearing colorectum, adenoma tissue, and normal mucosa from healthy volunteers were 435+/-392, 154+/-173, 295+/-202, 103+/-60 pmol CO2/h/mg protein, respectively. ODC activity of cancer tissue or adenoma tissue was significantly higher than that of the others. Among colorectal cancer patients, ODC activity in cancer tissue was correlated with T factors, lymph node metastasis and stages. Patients with tumors that had high ODC activity (> or =350 pmol CO2/h/mg protein) showed a poor 10-year survival rate. These results suggest that ODC activity may be a useful marker for patients' prognosis after surgery.

Pathogenesis of colorectal carcinoma and therapeutic implications: the roles of the ubiquitin-proteasome system and Cox-2

Pathways of the molecular pathogenesis of colorectal carcinoma have been extensively studied and molecular lesions during the development of the disease have been revealed. High up in the list of colorectal cancer lesions are APC (adenomatous polyposis coli), K-ras, Smad4 (or DPC4-deleted in pancreatic cancer 4) and p53 genes. All these molecules are part of important pathways for the regulation of cell proliferation and apoptosis and as a result perturbation of these processes lead to carcinogenesis. The ubiquitin-proteasome system (UPS) is comprised of a multi-unit cellular protease system that regulates several dozens of cell proteins after their ligation with the protein ubiquitin. Given that among these proteins are regulators of the cell cycle, apoptosis, angiogenesis, adhesion and cell signalling, this system plays a significant role in cell fate and carcinogenesis. UPS inhibition has been found to be a pre-requisite for apoptosis and is already clinically exploited with the proteasome inhibitor bortezomib in multiple myeloma. Cyclooxygenase-2 (Cox-2) is the inducible form of the enzyme that metabolizes the lipid arachidonic acid to prostaglandin H2, the first step of prostaglandins production. This enzyme is up-regulated in colorectal cancer and in several other cancers. Inhibition of Cox-2 by aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been found to inhibit proliferation of colorectal cancer cells and in epidemiologic studies has been shown to reduce colon polyp formation in genetically predisposed populations and in the general population. NSAIDs have also Cox-independent anti-proliferative effects. Targeted therapies, the result of increasingly understanding carcinogenesis in the molecular level, have entered the field of anti-neoplastic treatment and are used by themselves and in combination with chemotherapy drugs. Combinations of targeted drugs have started also to be investigated. This article reviews the molecular pathogenesis of colorectal cancer, the roles of UPS and Cox-2 in it and puts forward a rational for their combined inhibition in colorectal cancer treatment.